In apparatuses, such as industrial robots, which have movable parts that move relative to a machine main unit, cases often occur where it is necessary to install electric wiring between the machine main unit and the movable parts. In such cases, if electric cables connecting between the machine main unit and the movable parts are left in an exposed state, they are liable to be damaged e.g. by being brought into contact with external members, and hence there is a fear that cable disconnection or the like is caused. Further, also in a case where a main unit of a communication apparatus or an electronic apparatus and a movable unit thereof that can be pulled out of the main unit are electrically connected by cables, it is necessary to retain the cables so as to prevent the cables from being disconnected when the movable unit is moved in or out or to enable high-density packaging.
For this reason, to wire a plurality of cables, such as power wires and signal wires, to such a movable part that relatively moves, the cables are received and protected within e.g. a flexible cable retainer configured to have a chain-like shape. Such a chain-like cable retainer is formed such that it can change its shape according to relative movement of the machine main unit and the movable part, and hence it is possible to protect the electric cables from external members without causing adverse effects, such as interference with movement of the movable part.
As a conventional cable retainer, one disclosed in Japanese Patent No. 2589448 (Paragraphs [0016] and and FIG. 1) is known. Each of unitary link members constituting the cable retainer comprises a pair of side plate portions disposed in a manner spaced from each other by a predetermined distance in a horizontal direction, a bottom plate portion for connecting respective lower ends of the pair of side plate portions, and a beam member for partially closing upper portions of the side plate portions in a state in which cables, such as those of electric wires, are received between the pair of side plate portions so as to prevent the cables from coming out of the link member. The cable retainer is formed to be bendable, by fitting a cylindrical protrusion and a round hole formed at respective front and rear ends of ones of the link members to be coupled to each other. This prevents the cables from being damaged when routing them at the time of moving the movable unit into and out of the main unit, and also enable the cables to be smoothly moved thereafter. Therefore, it is possible not only to protect the whole cables but also to restrict uncontrolled movement of the cables themselves.
By the way, in such a conventional technique, the construction of a mold for forming each link member is simplified for reduction of the cost of the cable retainer. However, in the conventional cable retainers, each link member has a fixed space for passing a cable therethrough. Therefore, there are prepared many types of link members having respective different sizes or shapes in advance, and a wiring capacity is set according to wiring conditions of each cable retainer, whereby a link member having a size suitable for the wiring capacity is selected.
Assuming that the cable retainer is standardized without changing the structure of the conventional link member, in a case where the amount of cables is less than the space for passing the cables, a behavior of the cables becomes unstable due to a difference in wiring capacity, which may cause a problem such as cable disconnection.
Further, there is a case where the number of required cables may increase due to addition of a function to a device after being shipped. If cables the volume of which is more than the wiring capacity are inserted into the same cable retainer, the beam members which close the upper portions of the cable retainer may be damaged when the cable retainer is bent or may come off the side plate portions.
Therefore, due to a fixed volume of cables which can be accommodated in the link members of the conventional cable retainer, it is impossible to flexibly cope with an increase in the wiring capacity.